Do acetals and hemiacetals give positive 2,4 DNP test?

The reagent for the reaction is described as:

An aqueous solution of 2,4-dinitrophenyl hydrazine (DNP) is known as Brady's reagent

I recently learnt that acetal don't give positive tollens test whereas hemiacetals did. Following from the same conclusion I believe that since its an aqueous solution and seems alkaline aswell so according to me acetals should give negative 2,4 DNP Test whereas hemiacetals should give positive.

However I fail to find any literature on this, are my conclusions correct or are there any twists to it!?


1 Answer 1


The standard mixture for a 2,4-DNP test contains 2,4-DNP and conc. Sulfuric Acid in EtOH/water here. This is sufficient to hydrolyse most acetals and hemi-acetals so they will give a positive test. Cyclic acetals such as dioxolanes are more stable and may not.


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